The use of certain bromine, chlorine, and iodine containing halogenated chemical agents for the extinguishment of fires is common. These agents are in general thought to be effective due to their interference with the normal chain reactions responsible for flame propagation. The most widely accepted mechanism for flame suppression is the radical trap mechanism proposed by Fryburg in Review of Literature Pertinent to Fire Extinguishing Agents and to Basic Mechanisms Involved in Their Action, NACA-TN 2102 (1950). The finding that the effectiveness of the halogens are on a molar basis in the order Cl<Br<I supports the radical trap mechanism, as reported by Malcom I Vaporizing Fire Extinguishing Agents, Report 117, Dept. of Army Engineering Research and Development Laboratories, Fort Bevoir, Va., 1950 (Project-8-76-04-003). It is thus generally accepted that compounds containing the halogens Cl, Br and I act by interfering with free radical or ionic species in the flame and that the effectiveness of these halogens is in the order I>Br>Cl. In addition, it is generally thought that to be effective as a fire extinguishing agent, a compound must contain Cl, Br or I.
The use of iodine-containing compounds as fire extinguishing agents has been avoided primarily due to the expense of their manufacture or due to toxicity considerations. Until very recently, the three fire extinguishing agents presently in common use were all bromine-containing compounds; Halon 1301 (CF3Br), Halon 1211 (CF2BrCl) and Halon 2402 (BrCF2CF2Br). The effectiveness of these three volatile bromine-containing compounds in extinguishing fires has been described in U.S. Pat. No. 4,014,799 to Owens. Certain chlorine containing compounds are also known to be effective extinguishing agents, for example Halon 251 (CF3CF2Cl) as described by Larsen in U.S. Pat. No. 3,844,354.
Although the above-named bromine or chlorine-containing Halons are effective fire fighting agents, those agents containing bromine or chlorine are asserted by some to be capable of the destruction of the earth's protective ozone layer. Also, because the agents contain no hydrogen atoms which would permit their destruction in the troposphere, the agents may also contribute to the greenhouse warming effect.
More recently, hydrofluorocarbons have been proposed for fire suppression, for example in U.S. Pat. No. 5,124,053. However, a disadvantage of these compounds is their relatively high global warming potential.
Recently, ethers, particularly fluoroethers, have been identified as compounds that may be useful as halon replacements. Typically, these compounds are synthesized with all of the necessary fluorine content in place.
It is therefore an object of this invention to provide a method for extinguishing fires that extinguishes fires as rapidly and effectively as the techniques employing Halon agents while avoiding the above-named drawbacks.
It is a further object of this invention to provide an agent for the use in a method of the character described that is efficient, economical to manufacture, and environmentally safe with regard to ozone depletion and greenhouse warming effects.
It is a still further object of this invention to provide blends of the new agents and other fire extinguishing agents that are effective and environmentally safe.